(1) Field of the Invention
The present invention relates to a method and a device for detecting touch, e.g. by a finger touching a touch-surface of the device. In particular the invention relates to detection of touch by means of influencing, by means of the touch, propagation of light within the touch-sensitive device and detecting resulting change of light arriving to at least one detector device of the touch-sensitive device.
(2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
WO 2009/086836 discloses a device for detecting position of an object touching the device. The position of the object touching the device is detected by means of the object disturbing light guided by the device from a light source towards a detector and detecting the resulting change of light arriving to the detector. A position of touch may be determined on the basis of determination of two coordinates of a two-dimensional surface of touch. Thus, in order to determine a position of touch it is of importance that the object may disturb or influence light propagation relating to both coordinates sufficiently.
US 2004/252091 A1 discloses a touch panel in which two or more light sensors emit light into a transparent panel at an angle to sustain transmission through the panel by total internal reflection. The transmitted light is detected at an array of light detection positions around the periphery of the panel opposite to each light source.
US 2008/266266 A1 discloses surface acoustic wave touchscreens and infrared touchscreens that are installed over a display screen. The display screen may be a liquid crystal display, cathode ray tube, Plasma, organic light-emitting diode display, photographic image and the like. For an infrared touchscreen light emitting diodes or other transmitters are located proximate to outer edges of a touch area. The transmitters transmit infrared wave energy that is received by receivers. The receivers may be phototransistors. The receivers are located proximate to a horizontal/vertical side of the touch area opposite the transmitters. If based on infrared technology it may be desirable to provide a substrate for protecting the surface of the display screen.